Anaerobic adhesive systems are typically monomers which are stable in the presence of oxygen, but which polymerize in the absence of oxygen. Polymerization is initiated by the presence of a free radical generator such as a peroxy compound. The cured cross-linked resins are useful as sealants and as adhesives.
Typical resin monomers useful in anaerobic adhesive systems are terminated with polymerizable acrylate esters, such as methacrylate, ethacrylate and chloroacrylate esters. Another ingredient typically present is a polymerization initiator such as a free-radical mechanism initiator, preferably an organic hydroperoxide, such as cumene hydroperoxide, tertiary butyl hydroperoxide and the like. There is also normally provided a stabilizer against free radical initiation such as a quinone or hydroquinone, in an amount sufficient to prevent premature polymerization of the adhesive due to decomposition of the peroxy compound. There are also preferably present one or more accelerators which are typically organo-nitrogen-containing compounds such as tertiary amines, imides, sulfonamides and the like which promote the rate of cure. Cure can also be accelerated by the presence of a suitable metal, such as a transition metal, or its ion.
In application, an anaerobic adhesive is applied to one or both of the surfaces to be joined. When the two surfaces are joined and oxygen excluded, cure will be initiated. As is well known, surfaces such as glass may require application of a suitable accelerator such as a transition metal compound, which will increase the rate of cure on the substantial exclusion of oxygen or air. Anaerobic adhesives have been well published in the art as, for instance, in U.S. Pat. Nos. 2,895,950; 3,041,322; 3,043,820; 3,046,262; 3,203,941; 3,218,305; 3,300,547; 3,435,012; 3,547,851; 3,625,875; 3,993,815 and 4,039,705.
Anaerobic adhesive systems are typically supplied from a water-like liquid to a lightweight grease in consistency. One end use application is to apply the adhesives to the threads of a bolt or mating nut which are then assembled. The adhesive fills the spaces between the threads which excludes oxygen and enables cure in the normal situation. The metals present in the bolt or nut can accelerate curing.
As stated above, generally anaerobic adhesives are dispensed in a water-like liquid, a gel or grease form. It would be desirable to provide an anaerobic adhesive which can be dispensed as a tape. U.S. Pat. Nos. 3,993,815 and 4,039,705 describe anaerobic pressure-sensitive adhesive stocks which are in tape form. However, when such anaerobic adhesives are in such tape form, there is present some loss of the adhesive due to edge-ooze. Edge-ooze is the phenomena of the adhesive under pressure within a laminate structure being squeezed out of such structure due to its low viscosity. Additionally, conventional tape systems require a wide tape generally of at least 1/2 to 3/4 inch wide to prevent or inhibit oxygen from being absorbed along the edges of the adhesive, which oxygen later will inhibit curing of the adhesive. The wider tapes provide retention of some adhesive properties as absorbed oxygen does not reach the inner portions of the adhesive layer. Anaerobic adhesive films which are now used contain reinforcing fiber to prevent the adhesive from flowing off its carrier film. Such fiber is positioned within the adhesive layer and acts as a barrier to the flow of the adhesive. Generally, a plurality of fibers positioned parallel with the edges of the carrier film are used.
An anaerobic adhesive is desirable which has sufficiently high adhesive properties but which can be applied in the manner of a film or tape for easy application to articles to be joined and which exhibits decreased edge-ooze characteristics which in film or tape form. Additionally, it would be desirable to have such anaerobic films in varying widths without worrying about increasing curing time.